1. Field of the Disclosure
The present disclosure relates generally to audio amplification and more particularly to use of a general-purpose computer for pre-amplification in an audio signal path.
2. Background Information
In a typical high-end audio system, audio data from an audio source passes through several devices along an audio signal path, before being heard by a listener. Audio signals generally originate from a playback device, such as a compact disk (CD) player, Digital Video Disc (DVD) player, turntable, portable mp3 music player; or a receiver device, such as radio tuner or Internet interface. The audio signals may be analog or digital depending on the particular playback or receiver device used. The audio signals often pass to a pre-amplifier, which may be a discrete device or a portion of an Audio/Video receiver. A function of the pre-amplifier is to amplify possibly low-level, high impedance analog audio signals to “line-level,” an accepted signal strength usually stated in terms of decibel volts (dBV). Most commonly used consumer audio equipment has been adapted for, and work best with, a line-level of about −10 dBV, which corresponds to signals of about 0.3162 volts RMS.
In addition to converting analog audio signals to line-level, pre-amplifiers often apply equalization, tone control, and mixing/effects to both analog and digital audio signals. Equalization refers to the process of amplifying or reducing the level of audio signals in different frequency ranges, to remove irregularities introduced by components in the audio signal path. Such equalization may be implemented with a combination of low pass, high pass, band pass, and/or band stop filters. Tone control similarly involves changing the level of audio signals in selected frequency ranges, yet rather than attempt to correct for irregularities, tone control attempts to enhance audio sound by adding more of a desirable tone (amplifying the signal strength in those frequency ranges), or by reducing undesired tones (reducing the signal strength in those frequency ranges). Well known bass, treble, and graphic equalizer adjustments are examples of tone control. Finally, mixing/effects encompass a wide variety of simulated surround sound, environmental effects, soundscapes, and other complex manipulations of audio signals common in modern audio systems.
After pre-amplification, the audio signals are generally passed through an A/V Receiver, where switching functions are performed, as well as digital to analog conversion functions, if necessary. Then, the audio signals are passed to a power amplifier, which may be part of the A/V receiver, or, especially in high-end systems, a separate unit dedicated to power amplification. The power amplifier provides a current gain to the now analog audio signals, bringing the signals to a level of tens, or hundreds, of watts, so they may drive loudspeakers or other sound delivery devices. After this amplification, the analog audio signals are generally ready to be delivered to, and drive, sound delivery devices.
One shortcoming of a conventional audio signal path is its inflexible nature. Audio devices are generally purpose built and offer the user little possibility for customization or upgrade. For example, a conventional pre-amplifier may be configured to provide certain types of equalization and tone control, and a user may be able to select from among the types provided. Yet most conventional pre-amplifiers offer little opportunity to upgrade the device to obtain additional functionality, for example, via a software download from the Internet. Instead, a user must generally purchase a new pre-amplifier that has been hard-wired with the additional functionality. Similarly, many pre-amplifier have a variety of dials, readouts, and controls on a physical control panel, often the front panel of the unit. These are generally single purpose hardware devices. A user who purchases the pre-amplifier must accept their appearance and functionality, and may not customize or alter them in any way. Finally, conventional pre-amplifiers generally lack the ability to output audio-interactive graphics and images for display to a user. Many users find such graphics and images entertaining, and a desirable addition to their listening experience. While some users accept these limitations, other users desire greater flexibility, customizability, and graphics display in the pre-amplification stage of the audio signal path of their audio system.